Jeremy A. Arnold

Energy Efficiency of Hierarchical Server Load Distribution Strategies

Energy efficiency of servers has become a significant issue over the last years. Load distribution plays a crucial role in the improvement of energy efficiency as (un-)balancing strategies can be leveraged to distribute load over one or multiple systems in a way in which resources are utilized at high performance, yet low overall power consumption. This can be achieved on multiple levels, from load distribution on single CPU cores to machine level load balancing on distributed systems. With modern day server architectures providing load balancing opportunities at several layers, answering the question of optimal load distribution has become non-trivial. Work has to be distributed hierarchically in a fashion that enables maximum energy efficiency at each level. Current approaches balance load based on generalized assumptions about the energy efficiency of servers. These assumptions are based either on very machine-specific or highly generalized observations that may or may not hold true over a variety of systems and configurations. In this paper, we use a modified version of the SPEC SERT suite to measure the energy efficiency of a variety of hierarchical load distribution strategies on single and multi-node systems. We introduce a new strategy and evaluate energy efficiency for homogeneous and heterogeneous workloads over different hardware configurations. Our results show that the selection of a load distribution strategy depends heavily on workload, system utilization, as well as hardware. Used in conjunction with existing strategies, our new load distribution strategy can reduce a single systems power consumption by up to 10.7%.

How to Build a Benchmark

Standardized benchmarks have become widely accepted tools for the comparison of products and evaluation of methodologies. These benchmarks are created by consortia like SPEC and TPC under confidentiality agreements which provide little opportunity for outside observers to get a look at the processes and concerns that are prevalent in benchmark development. This paper introduces the primary concerns of benchmark development from the perspectives of SPEC and TPC committees. We provide a benchmark definition, outline the types of benchmarks, and explain the characteristics of a good benchmark. We focus on the characteristics important for a standardized benchmark, as created by the SPEC and TPC consortia. To this end, we specify the primary criteria to be employed for benchmark design and workload selection. We use multiple standardized benchmarks as examples to demonstrate how these criteria are ensured.

Analysis of the Influences on Server Power Consumption and Energy Efficiency for CPU-Intensive Workloads

Energy efficiency of servers has become a significant research topic over the last years, as server energy consumption varies depending on multiple factors, such as server utilization and workload type. Server energy analysis and estimation must take all relevant factors into account to ensure reliable estimates and conclusions. Thorough system analysis requires benchmarks capable of testing different system resources at different load levels using multiple workload types. Server energy estimation approaches, on the other hand, require knowledge about the interactions of these factors for the creation of accurate power models. Common approaches to energy-aware workload classification categorize workloads depending on the resource types used by the different workloads. However, they rarely take into account differences in workloads targeting the same resources. Industrial energy-efficiency benchmarks typically do not evaluate the systems energy consumption at different resource load levels, and they only provide data for system analysis at maximum system load. In this paper, we benchmark multiple server configurations using the CPU worklets included in SPECs Server Efficiency Rating Tool (SERT). We evaluate the impact of load levels and different CPU workloads on power consumption and energy efficiency. We analyze how functions approximating the measured power consumption differ over multiple server configurations and architectures. We show that workloads targeting the same resource can differ significantly in their power draw and energy efficiency. The power consumption of a given workload type varies depending on utilization, hardware and software configuration. The power consumption of CPU-intensive workloads does not scale uniformly with increased load, nor do hardware or software configuration changes affect it in a uniform manner.

The implementation of the server efficiency rating tool

The Server Efficiency Rating Tool (SERT) has been developed by Standard Performance Evaluation Corporation (SPEC) at the request of the US Environmental Protection Agency (EPA), prompted by concerns that US datacenters consumed almost 3% of all energy in 2010. Since the majority was consumed by servers and their associated heat dissipation systems the EPA launched the ENERGY STAR Computer Server program, focusing on providing projected power consumption information to aid potential server users and purchasers. This program has now been extended to a world-wide audience. This paper expands upon the one published in 2011, which described the initial design and early development phases of the SERT. Since that publication, the SERT has continued to evolve and has entered the first Beta phase in October 2011 with the goal of being released in 2012. This paper describes more of the details of how the SERT is structured. This includes how components interrelate, how the underlying system capabilities are discovered, and how the various hardware subsystems are measured individually using dedicated worklets.

Further implementation aspects of the server efficiency rating tool (SERT)

The Server Efficiency Rating Tool (SERT) has been developed by the Standard Performance Evaluation Corporation (SPEC) at the request of the US Environmental Protection Agency (EPA). Almost 3% of all electricity consumed within the US in 2010 went to running datacenters. With this in mind, the EPA released Version 2.0 of the ENERGY STAR for Computer Servers program in early 2013 to include the mandatory use of the SERT. Other governments world-wide that are also concerned by growing power consumption of servers and datacenters are considering the adoption of the SERT.

SPECpower_ssj2008: driving server energy efficiency

SPECpower_ssj2008 [1] is the first industry-standard SPEC [2] benchmark that evaluates the power and performance characteristics of volume server-class and multi-node class computers. This poster-paper gives an overview of the benchmark that defines the server power measurement standards [8] in the same way SPEC have done for performance.

Server efficiency rating tool (SERT)

The Server Efficiency Rating Tool (SERT) [1] has been developed by Standard Performance Evaluation Corporation (SPEC) [2] at the request of the US Environmental Protection Agency (EPA) [3], prompted by concerns that US datacenters consumed almost 3% of all energy in 2010. This poster-paper gives an overview of the SERT.

Autopilot: Enabling easy Benchmarking of Workload Energy Efficiency

Benchmarking of energy efficiency is important as it helps researchers, customers, and developers to evaluate and compare the energy efficiency of software and hardware solutions. Developing and deploying energy-efficiency benchmarking workloads are challenging tasks, as work must be able to be executed in a power measurement environment using an energy-efficiency measurement methodology.The existing SPEC Chauffeur Worklet Development Kit (WDK) enables the development and use of custom workloads (called worklets) within a standardized power measurement methodology. However, it features no integration in development environments, making building and deployment of workloads challenging. We address this challenge by proposing Autopilot, a plugin for the Eclipse IDE. Autopilot enables fast and easy building and deployment of a workload under development on a system for testing. It also enables benchmark execution directly from the development environment.

Server efficiency rating tool (SERT) 1.0.2: an overview

The Server Efficiency Rating Tool (SERT) has released the Standard Performance Evaluation Corporation (SPEC) and the EPA released Version 2.0 of the ENERGY STAR for Computer Servers program in early 2013 to include the mandatory use of the SERT. Other governments world-wide that are concerned with the growing power consumption of servers and datacenters are also considering adoption of the SERT. This poster-paper provides an overview of the current release of 1.0.2 version of SERT.

Measuring and Benchmarking Power Consumption and Energy Efficiency

Energy efficiency is an important quality of computing systems. Researchers try to analyze, model, and predict the energy efficiency and power consumption of systems. Such research requires energy efficiency and power measurements, as well as measurement methodologies. Many such methodologies exist. However, they do not account for multiple load levels and workload combinations. In this paper, we introduce the SPEC power methodology and the tools implementing this methodology. We discuss the PTDaemon power measurement tool and the Chauffeur power benchmarking framework. We present the SPEC Server Efficiency Rating Tool (SERT), the workloads it contains and introduce the industry-standard compute efficiency benchmark SPECpower_ssj2008. Finally, we show some examples of how the SPEC power tools have been used in research so far.